The invention relates to a tracking or grading unit for ski-trails and paths, the unit comprising a slide arrangement having at least one sliding or rolling front support and at least one sliding or rolling rear support or runner, and a frame upon which the front and rear supports are mounted, and having at least one cutting means, which is adjustable in height, arranged upon the frame and adapted to cut and/or break-up the snow cover.
A device of this type, having front runners and rear runners in the form of track runners, is disclosed in German OS No. 25 33 831.
The cutting device in this case consists of a digging blade, or the like, rigidly secured to the runner arrangement, the cutting speed and loosening effect thereof being dependent upon and limited by the speed at which the unit travels. Especially if the snow-cover is highly compacted and rutted, the performance of known units is in need of improvement. This is especially so if the constricted and awkward nature of the ground requires the unit to proceed at a relatively low speed. In addition to this, a device of the type mentioned requires a comparatively powerful drive for cutting highly compacted snow, especially if two trails are to be made or conditioned in one operation with double units having a large operating width.
It is therefore the purpose of the invention to provide a tracking or grading unit which permits intensive cutting, and possibly breaking-up, of the snow-cover, largely independent of the rate of travel and of the power of the tractor. According to the invention, this purpose is achieved, in the case of a unit of the type hereinbefore referred to by providing a cutting device with at least one motor-driven cutting tool, the cutting device comprising at least one pivot-arm mounted on the frame of the slide of runner arrangement, and at least one rotary cutting tool arranged at the lower end thereof.
Although a design of this kind is generally used mainly for producing trails and repairing them, the unit may also be used in principle for grading paths, e.g. for a departure run, since the motor-driven cutting tool makes it possible to operate over a relatively large width without impairing the intensity of the work done on the snow-cover.
In any case, what is important is the ability to level short elevations and depressions in the snow-cover, due to the direct mounting of the frame with the front and rear supports arranged relatively close together. This short support-length for the cutting tool allows an almost tangential adjustment and cutting path for longer undulations which cannot be smoothed out with the more intensive removal of shorter undulations.
It is desirable, according to the invention, especially when heavy pressure forces are involved, to provide an adjustable extension limit, in order to avoid deep penetration of the cutting tool and the production of uneven stretches in locations where the snow-cover is soft. It is also of advantage, in maintaining a particularly level trail-surface or path-surface, if a preload is provided for the cutting tool, with a limit-stop acting in the direction of extension of the tool. The result of this is that the pressure resulting from removal of relatively steep elevations, when the cutting tool lifts off the limit-stop, increases sharply in relation to the lift, thus producing particularly intensive action upon the snow-cover at the summit of an elevation.
It has been found particularly advantageous to adjust the height of the cutting tool with a handle in the form of a pivotable lever, comprising a series of locking positions corresponding to the height adjustments. This makes it possible to use a fixed operating position of the cutting tool, such as exists even during relatively high pre-loading in extension towards a stop, as long as the upwardly directed reaction-force, acting upon the tool, does not exceed the preload force plus the weight of the tool and of its mobile holder. The height adjustment may therefore also be used in principle even with a toolholder which is movable in operation.